1. Field of the Invention
This invention relates generally to systems and methods for image acquisition and, more specifically, to systems and methods for angiogenesis imaging using computed tomography.
2. Background of the Invention
Each year, many women are diagnosed with breast cancer, and the number of deaths associated with breast cancer has reached 40,000 per year. The death toll cannot be substantially reduced because current screening and diagnostic techniques do not detect all cancers at an early enough stage to effectuate a treatment cure. As such, early diagnosis and treatment of breast cancer is highly desirable.
Tumors larger than a few millimeters in cross section generally require a blood supply in order to obtain nutrients and oxygen for growth. Vessels that grow around the tumors proliferate in a disorganized manner and they may leak and pool blood around the tumors. Iodine-contrast-enhanced mammography has been used to detect tumors in women's breasts. In such procedure, contrast agent is introduced into a patient's vessel, and mammograms of the patient's breast are obtained before and after the contrast injection. By digitally subtracting the pre-injection image from post-injection images that are obtained over a time period of 1 to 7 minutes, a composite image can be obtained that shows tumor blood supply and “pooling” in the vicinity of the tumor. However, the contrast resolution of mammography is usually limited, and malignancies in tissues that are below 5 millimeters in cross-sectional dimension may not be detectable.
In order to create the composite image, the post-injection images obtained over the prescribed time period need to have a same image registration with the pre-injection image such that a pixel in the post-injection images can be processed with a corresponding pixel in the pre-injection image. Sometimes, a portion of the patient being imaged may move, e.g., translates 1 to 400 microns and/or rotates 1 to 2 degrees, when between images are taken. In such cases, a physician would need to realign the two images. If the pre-injection image and the post-injection images cannot be realigned or registered, the image collection procedure will need to be repeated. Usually, in a mammography procedure, a patient's breast is compressed by a set of paddles to reduce movements of the breast while pre-injection and post-injection images are obtained. However, patients usually experience discomfort from compression of the breasts. The discomfort can become so severe that the imaging procedure is terminated. In addition, the use of paddles to compress breast tissue restrict blood flow into the breast, thereby limiting an amount of contrast agent that can be delivered into the breast. This in turn, interferes with the kinetics of the contrast agent, and makes angiogenesis imaging difficult.
For the foregoing, improved systems and methods for imaging angiogenesis are desirable.